MRI and spinal tap. Progressive multifocal leukoencephalopathy has a characteristic appearance on on a brain mri. A lumbar puncture (spinal tap) is used to look for the virus that causes it.
Difficult perhaps. Pml mostly associated with immune deficiency and seen in HIV pts and with cancer patients on chemotherapy, but also with ms pts who are taking tysabri (natalizumab). Can do a blood test, anti-jc virus antibody, and spinal fluid dna screen or pcr, but MRI films may show characteristic patterns.